I wrote a short paper about this interaction, taking the perspective of both the foreign and domestic student bodies. I'll jot down some of the main conclusions.

Domestic students were typically held back he the language barrier. They couldn't communicate with many foreign students and found that the foreign students never made an effort to even try to communicate. When I spoke to a foreign student, she said that it is rare to find a student who actually wants to learn English to a level capable of casually speaking with an American classmate. Many foreign students just want to get their degree and go home.

The international Chinese student body I'd also growing in the US. Because China's middle class is expanding, more parents are able to send their child to the US for college. Because each campus now has more foreign students, these students can stick together and are not forced to interact outside of their culture and language. This solidifies the segregation.

From personal experience, there are students who work hard and participate and students who take short cuts and fake their way through class. This is true of any body of people. If the two Asian students are speaking in their native language in the corner while your group is working on a lab, it's much easier to notice them not doing any work as opposed to a student who sits quietly, copying down somebody's answer. The chatting of the foreign students may also be a distraction whereas the quiet plagiarizer doesn't directly hold back the group.

From the University's perspective, the University may try to promote diversity and accept many foreign students as well as offer English classes for these students. Having global connections as a university is a good thing for the school. The student body generally wishes that the university would have more strict English requirements because it would promote better cooperation between foreign and domestic students. Just offering more English classes would not be helpful because of the previously mentioned fact that many foreign students do not care to learn English.

In terms of cheating, I myself thought that the international students did cheat and quite extensively. This may have a bias towards the classes I was in. What I found was that most students hadn't seen an international student cheating. And many students didn't mind if they did, which I personally found very interesting. But a fair amount of students had heard of cheating among international students so this probably means that a few students witness cheating by the foreign students and become upset by it so they tell their classmates and peers and the news spreads. The cheating may or may not be as bad as it seems, I don't know the exact answer for that.

I know this doesn't answer all the questions you had but I hope it gives you an idea of what goes on between foreign and domestic students.

Tl;dr: for my university, it's widely held that the foreign Chinese students self segregate themselves because of language skills. There are lazy students and cheaters in any student body. And these tensions are faced by any University that tries to diversify.